Reserve replacement from governor to energy storage system on conventional generator for operating-cost reduction

This paper proposes an operation strategy for a steam turbine generator (GEN) with a built-in energy storage system (ESS) that replaces the role of the governor. The proposed strategy cuts the operating cost of GEN by minimizing the throttling loss and the amount of fuel with the harmonious operation of ESS. For the conventional governor droop control, the valve cannot be fully open for emergency release; it causes losses in the throttle valve and fuel cost due to the reserve. Beyond these limitations, in the proposed coordinated operation between GEN and ESS, the GEN can operate in the natural sliding pressure mode, which fully opens the steam turbine valves, reduces the steam pressure, and improves the efficiency of the turbine by minimizing the throttling loss. In this method, while a generator produces constant power without the reserve for an emergency condition in the proposed coordinated operation, an ESS is in charge of fast primary frequency control. Subsequently, the GEN can achieve a replaced reserve operation by ESS, which removes the constant operational loss by reserved steam and provides economic advantages by reducing operation costs. We theoretically demonstrate that the proposed operation provides a quick and reliable frequency control performance through frequency- and time-domain analysis compared with the conventional operation. Using a power generation simulator practically installed at Korea Western Power Co., Ltd., we also proved that the proposed operation can yield the economic benefit based on the cost reduction by minimizing losses of GEN, and provide an improved frequency regulation performance with the coordinating operation.